well to me it sounds like pieces of the puzzle are missing. unless your wife is uber controlling/not logical, there must be some reason why she feels this way. and of course you dont want to see your mother the way your wife does so it might be totally out of the blue for you.

is she being reasonable with her assumption that your mom is a bad influence? what exactly does your mom do to be this bad influence? have you tried talking to you mom about your wife's objections and if so, how does she feel about them?

you need to think about which relationship is unhealthy for you at this time. if you look at your relationships from the outside for a second and see that your wife if totally out of line then concentrate on that. but dont be afraid to look at how your mom acts, just because shes your mom. i had to cut off ties with my dad for about 2 years because i just couldnt take it anymore. you need to do whats best for you because if things with you arent right, that travels to your son as well. you need to focus on what you need in your life and stick with that. but dont be afraid to look at both your wife and your mom. hope this helps.